Entry port member for dip crucible apparatus



Jan. 28, 1969 J, E, BY RNE ET Al. 3,424,130

ENTRY PORT MEMBER FOR DIP CRUCIBLE APPARATUS Filed March 6, 1967 F I G3.

46 I, IN VENTURE. c/USEPH 15'. 5 news,

52 WILL/AM G MorrArr A TTOKA E Y 52 48% 50 BY wax/gr"? I United StatesPatent 4 Claims ABSTRACT OF DISCLOSURE In accreting molten material ontoa continuous, elongated core, the core is passed upwardly through acrucible containing a molten bath of the material. An entry port in theform of a cylindrical bushing is positioned in the bottom wall portionof the crucible through which the core is passed. The entry port isprovided with relatively short land section having internal parallelsurfaces extending from the upwardly disposed opening, and a secondsection having internal wall surfaces diverging from the land sectionterminating at the downwardly disposed opening thereby defining anopening of larger diameter than the upwardly disposed opening.

The dip forming process, such as used in casting metal, is now wellknown in the art. According to this process, an elongated body such as ametal rod is typically pretreated by passing it through a straightener,a surface cleaning apparatus and desirably through a drying means, andthen through a vacuum entrance chamber positioned below or at the bottomof a crucible containing a bath of molten material. A continuous,elongated core or body is passed upwardly through the molten bath, whichbath may have the same chemical composition as that of the core or adifferent composition. The molten material in the crucible accretes ordeposits upon the outer surface of the core thereby increasing itscross-sectional area appreciably. After emerging from the crucible, theresulting cast member is cooled as by a water spray from one or more jetnozzles at least sufiiciently so that the cast member can be rolled orworked. From there, the cast member may be passed through a suitableroll mechanism where it is drawn and reduced in cross-sectional area andthen passed to a suitable receiving means such as a take-up reel.

In the dip forming process, the core is fed from the vacuum entrancechamber through an entry port in the bottom wall of the crucible andinto a bath of molten material. This core entry port member is in thegeneral form of a cylindrical bushing inserted in the bottom wall of thecrucible. As practiced in the dip forming of copper for the productionof copper rod, the crucible is constructed of graphite and the entryport member or bushing is made from a refractory metal such asmolybdenum. An entry port useful in dip forming apparatus is disclosedin US. Patent Nos. 3,008,201, and 3,060,056, both assigned to theassignee of this application.

Typically in the dip forming process the core entry port member orbushing has been in the form of a relatively thin wall cylinder havingstraight and parallel internal and external cylindrical surfaces. It isdesirable to maintain a minimum clearance between the core and theinside surface of the bushing. However, the core is usually undulatingor wavy, and if the internal surfaces of the bushing are parallel,mechanical jamming occurs due to friction between the core and bushing.On the other hand, a significantly larger clearance can cause jammingdue to major penetration of the molten metal into the clearance space.

The long, parallel surface on the interior of the bushing and therelatively tight fit between it and the core result 3,424,130 PatentedJan. 28, 1969 in high frictional forces between the core and thebushing. This causes mechanical jamming and definitely demands theaction of a substantial pushing force on the core rod beneath thecrucible and/or a substantial tensile force on the emerging hod rod, allcreating undesirable effects. Such a tight fit over a continuouselongated core also results in larger heat losses from the cruciblethrough the bushing to the core.

This invention has, therefore, as its primary object to provide an entryport member for a dip crucible apparatus which substantially eliminatesmechanical jamming of the core upon entry to the crucible. This,together with other objects and advantages, may best be understood byreferring to the following detailed description, and to the accompanyingdrawings, in which:

FIGURE lillustrates, partly in section, a dip forming apparatusincluding the crucible having incorporated therein the improvement ofthe present invention;

FIGURE 2 is a sectional view of a portion of the crucible shown inFIGURE 1 illustrating in greater detail the entry port memberincorporated into the dip crucible apparatus; and

FIGURE 3 is a longitudinal sectional view of the entry port member ofthe present invention.

In the drawings, there is shown a preferred embodiment for practicingthe invention, and although the invention is described hereinbelow withparticular reference to forming copper rod, it should be understood thatthe invention is applicable for producing other stock such as sheet,tube or strip and of other materials or metals. Referring to FIGURE 1, acontinuous core rod of copper 10 is introduced to a drawing apparatus 12and shaving equipment 14 where the oxide coating or other surfacecontaminants are removed therefrom. If desired, other means may beutilized for cleaning the surface of the rod. The rod is passed throughdrive means 16 into tube 18 which may have connected thereto exhausttube 20 and evacuating pump 22 to maintain a vacuum in the members 12,14, 16 and 18, thereby avoiding the formation of an oxide coating on thecleaned rod. An entry port member or bushing 24, described hereinbelowin greater detail, is positioned in the bottom of crucible 26 whichcontains a molten bath of copper 28, and the core rod is passed upwardlythrough the bushing into the crucible. The molten copper is supplied tothe crucible from a suitable source such as an electric induction heatedfurnace (not shown), and the crucible is maintained at the desiredtemperature by suitable heating means such as an electric inductionheater 30. An inert atmosphere of dry nitrogen is introduced underpressure from source 32 into the crucible above the molten bath througha supply line 34. As the rod passes through the molten bath of metal inthe crucible, molten copper accretes progressively thereon therebyforming a rod of increased diameter with molten metal substantiallybonded to the core rod. (See FIG- URE 2.)

An elongated tube 36 extends upwardly from the crucible 26 and theresulting cast rod having copper accreted thereto is passed out of thecrucible through the extension tube. The cast rod emerging from thecrucible and extension tube is at a relatively high temperature and iscooled somewhat by cooling means 38, such as a water spray nozzle,before the rod is passed through a regulated drive motor 40 desirablyhaving incorporated therein a suitable shock isolation loop. From there,the cast rod is directed to a suitable drawing apparatus and storagearea as desired.

Referring now to FIGURES 2 and 3, a cylindrical, open-ended bushing 24is positioned in the bottom Wall portion of crucible 26. Desirably, aboot 41 is provided as spacing means between tube 18 and crucible 26.The bushing is provided with a relatively short land or first section 42having internal parallel surfaces extending from the top opening 44 ofthe bushing. (See FIGURE 3.) The land or first section is provided witha diameter sufiicient'to provide clearance between the core rod and theinside surface of the bushing. A second section 46 extends from the landand is provided with diverging internal wall surfaces terminating at thebottom opening 48 of the bushing. In this manner, the bottom opening isof a substantially larger diameter than the top opening. It is desirableto provide the internal wall surfaces of the second section with arcuatetermini 50 to facilitate feeding of the core rod into the bushing andcrucible. Also, the bushing is provided with an outwardly directedannular flange 52 at or near the bottom for connection to exhaust tube20 by means of clamps, bolts or other fastening elements. In thismanner, a tight fit is provided between the bushing and the exhaust tubethereby assuring a good connection for maintaining a vacuum.

The land should not extend for more than one-fourth the total length ofthe bushing, and preferably should be about one-eighth to one-tenth ofits total length. If the land is too long, the undulating core will jamin the bushing, as explained above. On the other hand, if the land istoo short such that the internal surfaces of the bushing terminate atthe upwardly disposed opening at too sharp a projection or point, moltenmetal penetrating the clearance will either freeze at the point andconsequently tear the core rod or drip down through the bushing into theexhaust tube where it could eventually freeze and cause considerabledifficulty. By reason of the present invention, a core rod havingundulations will pass through the bushing. The diverging wall surfacesin the second section of the bushing substantially eliminates mechanicaljamming of the core in the bushing. In addition, eliminating the long,parallel surfaces on the interior of the bushing reduces heat lossesfrom the crucible through the bushing to the core.

A typical blushing found to be particularly useful in the dip formingprocess for forming copper rod, such as illustrated in FIGURE 3, mayhave an overall length of about 2.3 inches. The land section is aboutone-fourth inch in length and the internal diameter of the land is about0.38 inch. The second section is provided with a diameter at thedownwardly disposed opening of about 0.41 inch. The bushing may be madefrom molybdenum or other refractory metal, and the internal wallsurfaces are provided with a high polish, the land desirably having thehighest polish.

We claim:

1. In a dip forming crucible apparatus adaptable for containing a moltenbath of metal and including a substantially cylindrical, open-endedbushing disposed in the bottom wall portion thereof, whereby acontinuous metallic core member of extended length introduced to saidcrucible is passed upwardly through said bushing into said bath wheresaid molten metal accretes to said core member, the improvementcomprising: said bushing including a first section having internalparallel surfaces extending from the upwardly disposed opening of saidbushing for a distance not more than one-fourth the length of saidbushing, said first section having a diameter sufficient to provideclearance therethrough of said core member, and a second section havinginternal wall surfaces diverging from said first section and terminatingat the downwardly disposed opening of said bushing to define an openingof larger diameter than said upwardly disposed opening, therebysubstantially eliminating jamming of the core member in said bushing.

2. Apparatus according to claim 1 wherein said internal wall surfaces ofsecond section have an arcuate termini.

3. Apparatus according to claim 1 wherein said first section extends fora distance of from one-eighth to onetenth of the total length of saidbushing.

4. In a dip forming crucible apparatus adaptable for containing a moltenbath of metal and including a substantially cylindrical, open-endedbushing disposed in the bottom wall portion thereof, whereby acontinuous metallic core member of extended length introduced to saidcrucible is passed upwardly through said bushing into said bath wheresaid molten metal accretes to said core member, the improvementcomprising: said bushing including a first section having internalparallel surfaces extending from the upwardly disposed opening of saidbushing for a distance of from about one-eighth to one-tenth the lengthof said bushing, said first section [having a diameter sufficient toprovide clearance therethrough of said core member, and a second sectionhaving internal wall surfaces diverging from said first section andhaving arcuate termini at the downwardly disposed opening of saidbushing to define an opening of larger diameter than said upwardlydisposed opening, thereby substantially eliminating jamming of the coremember in said bushing.

References Cited UNITED STATES PATENTS 1,870,990 8/1932 Evans 118-405 X2,341,450 2/1944 Knaus 118405 2,347,392 4/1944 Bouget 118-40'5 X3,227,577 1/1966 Baessler et al. 118-405 X WALTER A. SCHEEL, PrimaryExaminer.

JOHN P. MCINTOSH, Assistant Examiner.

